This time is different: the source code is available from the “live” repository the ASP.NET team is working on, and they are going to accept pull requests (if of course the quality of the submission is good and it adheres to the roadmap for the release). And it’s not just ASP.NET MVC, but also the WebAPI, the Razor view engine, and ASP.NET Web Pages.

This means that one can build the frontend part of a web site/web application with Open Source libraries from Microsoft or officially supported by Microsoft (like jQuery, jQuery UI, Knockout.js, JSON.net, upshot). To make it complete the system.web dll would have to be opensourced as well, but that would mean the whole .NET framework should be opensourced.